Field of the Invention
The present invention relates to a stent for medical use that is indwelled inside a bile duct or a pancreas duct for use.
Description of Related Art
In the related art, a stent for medical use (hereinafter, also referred to as a “stent”) has been used to expand a narrowed area formed in a bile duct or a pancreas duct and maintain patency while being indwelled in the narrowed area.
Examples of such stents are known from Japanese Patent No. 4981994 and Japanese Unexamined Patent Application, First Publication No. H11-76412. The stent disclosed in Japanese Patent No. 4981994 includes a coil (a reinforcement portion) which is formed by winding a strand about an axis, an outer layer which is formed in a substantially tubular shape and is provided at the outer peripheral side of the coil to be coaxial with the coil, and an inner layer which is formed in a substantially tubular shape and is provided at the inner peripheral side of the coil to be coaxial with the coil.
Four flaps (locking members) are fixed to the outer layer at equiangular intervals about the axis and located at an outer circumferential surface of a portion serving as a distal end side portion when the stent is inserted into a bile duct. Each flap has elasticity. When the flap is pressed inward in the radial direction of the outer layer, the flap is received in a notch portion formed in the outer layer.
Even at an outer circumferential surface at a proximal end side of the outer layer, the four flaps are similarly fixed at equiangular intervals about the axis.
The strand of the coil is provided at the constant pitch in the axial direction from the distal end side in relation to a portion to which the distal end side flap is fixed to the proximal end side in relation to a portion to which the proximal end side flap is fixed.
When a stent with such a configuration is indwelled inside a bile duct, an endoscope is inserted from a mouth or the like into a patient's body cavity, and a distal end of the endoscope advances to the vicinity of a duodenal papilla. The stent is inserted into a channel through a forceps opening of the endoscope, and is inserted into the bile duct while the stent is observed fluoroscopically. When the stent reaches a narrowed area of the bile duct, the distal end side flap is closed while being pressed by the narrowed area and is received in the notch portion. When the distal end side flap advances beyond the narrowed area, the flap is opened due to the release of the pressure applied from the narrowed area to the flap. Accordingly, the distal end side flap is locked into the narrowed area. The proximal end side flap locks the duodenal papilla. In this state, the stent is indwelled inside the narrowed area for a predetermined period of time.
Since the stent is provided with the coil, it is possible to suppress the indwelled stent from being crushed in the radial direction. Accordingly, it is possible to maintain a space inside a tube conduit of the stent and to cause bile to easily flow through the narrowed area.
While the stent is indwelled in the narrowed area, a component such as bile accumulates on an inner peripheral surface of the stent, and hence the tube conduit thereof is narrowed. When this happens, the indwelled stent is collected to be replaced by a new stent. The collection of the stent is performed when the stent moves (erroneously moves) from the position at which it is indwelled.
The stent is mainly replaced by the following methods.
A first method is a method of gripping a stent with a gripping tool inserted through a channel of an endoscope and extracting the endoscope to an outside of a body along with the gripping tool gripping the stent. In this case, there is a need to insert an endoscope into a patient again in order to insert a new stent into a body cavity.
A second method is a method (TTS: Through The Scope) of gripping a stent with a gripping tool inserted through a channel of an endoscope and extracting the stent and the gripping tool to the outside of a body through a channel while the position of the endoscope is fixed. The second method has an advantage that a burden on the patient is small and an operator's burden is also small compared to the first method.
In the stent which is indwelled for a predetermined period, the tube conduit is narrowed, and hence the inside of the tube conduit is not easily gripped. For this reason, the proximal end side outer circumferential surface of the stent is gripped by a gripping tool or is squeezed and vibrated by a snare. In order to reliably hold the stent with the gripping tool or the snare, there is a case in which the gripping tool or the snare is locked to the center portion of the stent in relation to the proximal end side flap of the outer layer. In Japanese Patent No. 4981994, the stent which is indwelled for a predetermined period needs to be collected while the proximal end of the stent is gripped. When the stent is led into the channel, the held portion of the stent first enters the channel, and the distal end side portion and the proximal end side portion in relation to the held portion of the stent subsequently enter the channel. That is, the stent is led into the channel while being folded back at the held portion.